The long range objective of this project is to study the mechanism controlling the expressing of endogenous viral genes by normal physiological stimuli such as hormones. Present studies include: (1) the characterization of viral precursor molecules found in the NIH Swiss mouse uterus following estrogen stimulation; (2) the influence of age and hormone on end organ expression of virus information; (3) the mechanism of RNA-directed DNA polymerase and viral 70S template-primer interaction; (4) the comparison of DNA polymerases from several different type C RNA viruses; (5) the relationship between endocrine changes produced by ovariectomy and adrenal carcinoma in aged NIH Swiss mice.